Spectacles and associated methods for presbyopia treatment and myopia progression control

ABSTRACT

Presbyopia treatment and anti-myopia spectacles comprise a negative refractive element facing an object and a positive refractive element facing a patient eye. The negative refractive element has a central zone with a strong negative refractive power. The positive refractive element has a central zone with a less strong positive refractive power. The front focal point of the central zone of the positive lens does not have to overlap with the front focal point of the central zone of the negative lens. The negative refractive element and the positive refractive element are axially separated by a relatively small distance such that the combination of the two refractive elements is compact enough to be made into an easily wearable spectacle. For myopia progression control, at least one portion of the paracentral and/or peripheral zone of at least one of the two refractive elements has a relative add power with respect to that of the central zone such that the image of an off-axis distant or intermediate object is formed in front of a corresponding paracentral or peripheral retina area to create myopic defocus on the corresponding retina area.

CROSS REFERENCE TO RELATED APPLICATION

This non-provisional application claims the benefit of U.S. provisionalapplication No. 62/649,669 of the same title, filed in the USPTO on Mar.29, 2018, by inventors Yan Zhou et al., which application isincorporated herein in its entirety by this reference.

FIELD OF THE INVENTION

One or more embodiments of the present invention relate generally topresbyopia treatment and/or myopia progression control or prevention. Inparticular, the embodiments are related to the design of presbyopiatreatment and anti-myopia progression spectacles.

BACKGROUND

With the popular use of personal computers and mobile cell phones byyoung children, the percentage of school children developing myopia hasincreased substantially in the past couple of decades. The onset ofmyopia also occurs at younger ages as compared to the time beforepersonal computers and mobile cell phones were popular. Although thecause and treatment of myopia have been debated for decades, the exactmechanism of myopia development still remains unclear. However, recentclinical studies have shown that myopia progression can be slowed andcontrolled. In addition to treatment using pharmaceutical substanceslike atropine and pirenzepine, another clinically proven approach is tooptically extend the depth of focus (or field) by making both distantand nearby objects in focus such that demand for sufficientaccommodation is substantially reduced. Still another clinically provenapproach is to optically induce paracentral and/or peripheral myopicdefocus on the retina, i.e. with sharply focused image of a distantobject formed on the fovea or macula, and with paracentral and/orperipheral image shell of a distant off axis object formed in front ofthe retina.

In addition to reshaping the cornea using, for example, orthokeratology(Ortho-K) to achieve at least one of the two optical effects, many lensdesigns that produce at least one of the two optical effects have beendisclosed to the public. They include different types of progressiveaddition lenses (PALs), bi-focal lenses, multi-focal lenses, progressivemultifocal lenses, and extended depth-of-focus lenses.

Most of these lenses are contact lenses comprising one optical element.An issue with the use of a contact lens is that when children arerelatively young (for example, from about 5 years to about 8 years old),they may not be mature enough to be trained to safely put contact lenseson their eyes by themselves. For this group of children, to both correcttheir refractive error(s) and also slow or stop their myopiaprogression, it is more desirable to offer them an anti-myopiaspectacle.

Towards this need, there are so far only a couple of commerciallyavailable anti-myopia progression spectacles that have beencommercialized to offer myopia progression control, including theMyoVision spectacle from Zeiss and the Myopilux spectacle from EssilorInternational. These spectacles have been found to offer only limitedefficacy in terms of myopia progression control. For example, the ZeissMyoVision spectacle lens has been clinically found to be only effectivefor children who have myopic parents and the average reduction to myopiaprogression is only about 30% as compared to a control group. TheMyopilux Max spectacles claim to have slowed down myopia progression byup to 62%, but only for exophoric children with properly measured andprescribed prismatic bifocal correction. In the case of EssilorInternational's Myopilux Pro, a progressive addition lens speciallydesigned for esophoric kids, the claimed percentage in myopiaprogression reduction is only 38%.

Therefore, a need exists for an improved design of an anti-myopiaprogression spectacle that will reduce the need for large accommodationor demand less accommodation and at the same time can provide clinicalefficacy for all myopic children with at least an efficacy comparable tothat of some high performance anti-myopia contact lenses or the Ortho-Kapproach.

SUMMARY

One or more embodiments of the present disclosure satisfy one or more ofthe above-identified needs in the art. In accordance with the presentinvention, modified and rearranged lens elements from a reverse Galileantelescope can be incorporated into a wearable Increased ResolvableObject Distance Range (IRODR) spectacle that can simultaneously providea number of optical properties beneficial for either presbyopiatreatment or myopic progression control.

In one embodiment of the present invention, a pair of IRODR lenscombinations are made from high index and light weight material isdesigned as and made into a spectacle to be worn by a patient sufferingfrom presbyopia and/or myopia. The central zone of a negative refractiveelement and the central zone of a positive refractive element aredesigned to have a much stronger refractive power than a conventionalreverse Galilean telescope. These choices can ensure a short relativedistance (preferably less than 30 mm) between the two elements of theIRODR lens combination, thus making the design compact and light enoughto be practically wearable by a patient, especially a child.

A second modification is in the weakness of the optical minimizationeffect for the central zone when viewing a distant object. Aconventional reverse Galilean telescope generally minimizes a distantobject by a multiple times. In contrast, with IRODR lens combination,the image size change for near and also far objects is within ±50%. Withsuch a design, a nearby object, when viewed by a patient wearing such anIRODR spectacle, will not experience significant size change while beingoptically pushed further away from the eye.

A third modification is in the net central refractive power. While aconventional reverse Galilean telescope generally has a zero netrefractive power, i.e. the front virtual focal point of the negativelens basically overlaps with the front real focal point of the positivelens so that a collimated beam entering the optical system will come outcollimated with its beam width reduced, the presently disclosed IRODRlens combination does not have the front focal points overlappinglimitation and instead, it has a central zone with an intended netcentral refractive power to correct the refractive error(s) of a patienteye such that a distant or intermediate or near object can be sharplyfocused on the fovea or macula while the depth of field is substantiallyincreased.

A fourth modification is in the spatial refractive power distributionover the full spectacle lens area. Instead of keeping the net refractivepower relatively constant over the whole area, the spatial refractivepower distribution is intentionally made not to be the same. For myopiaprogression control, at least one portion in a paracentral and/orperipheral zone of the IRODR spectacle is made to have a net add or plusrefractive power relative to that in the central zone. This feature willmake at least a portion of the image shell of a distant or intermediateobject land in front of the paracentral and/or peripheral retina, thusinducing myopic defocus on the paracentral and/or peripheral retina tocontrol myopia progression.

There are also a number other features and/or modifications associatedwith different embodiments of the present invention. Resulting from atleast one of these features and/or modifications, the IRODR spectaclecan substantially increase the depth of field (or focus) by opticallypushing nearby object away and optically bringing distant object closer,thus providing the capability to not only correct refractive error(s)but also control myopia progression, as well as treat presbyopia.

One object of the present invention is to optically push a nearby objectfurther away from a patient eye. This will cause a nearby objectoptically to be no longer as near or close to the patient eye. Becauseof this, the nearby object is no longer perceived as blurred by even apresbyopic eye that does not have any accommodation capability. In thecase of a person having accommodation capability, the amount ofaccommodation required to bring such a nearby object to sharp focus onthe retina can be substantially reduced.

Another object is to effectively reduce the entrance pupil size andhence further increase the effective depth of field (or focus). As aresult, objects within a larger distance range can be perceived by apatient as in focus even without accommodation, which will furtherreduce accommodative stress to thereby slow or retard or limit theprogression of myopia.

Still another object is to create a certain degree of tunnel vision tolimit ocular movement while increasing the angular field of view in theobject space such that the most effective retina area in terms of myopiaprogression control can be fully utilized.

Still another object is to make the IRODR spectacle easily adjustable interms of providing fine tuning of the net effective refractive errorcorrection power by controlling the relative distance between the tworefractive elements in a continuous manner. As a result, fewer discreterefraction power step lenses are needed to cater for a large patientpopulation, thus saving cost.

Still another object is to make the IRODR spectacle automaticallyadjustable in terms of providing indoor near vision and outdoor distantvision net effective refractive error correction powers by embedding alight sensor and a solar cell or battery together electronics (andfirmware if needed) in the spectacle to activate a change in therelative distance between the two refractive elements.

In one embodiment, the negative lens is a plano and aspherical concavelens, and the positive lens is a spherical convex and plano lens. Such adesign will have a net positive spherical aberration and hence induceparacentral and/or peripheral myopic defocus on the retina, desired formyopic progression control.

In still another embodiment, instead of minimizing optical distortion,optical distortion is intentionally created by manipulating the spatialdistribution of refraction to either induce specially rendered myopicdefocus on the paracentral and/or peripheral retina and/or to changeoptical magnification or demagnification from the central zone to theparacentral zone to the peripheral zone.

Another aspect of the present invention is to make the first surface ofthe negative lens on the object space side relatively flat or much lesscurved and the second surface of the negative lens strongly curved, andalso to make the first surface of the positive lens strongly curved andthe second surface of the positive lens that faces the patient eyerelatively flat or much less curved. This way, the outer surfaces of theIRODR lens combination are relatively flat and easy to clean while thetwo strongly curved surfaces are contained within the IRODR lenscombination.

Still another aspect of the present invention is to have the paracentraland/or peripheral region of either the negative lens or the positivelens or both lenses formed like a Fresnel lens such that the overallthickness of the lens(es) can be made substantially thinner. Theparacentral and/or peripheral Fresnel lens portion(s) is(are) preferablyformed on the strongly curved surface(s).

In one embodiment, the paracentral and/or peripheral Fresnel lensportion is made of multiple rings or race tracks with radiallyincreasing relative power addition. In another embodiment, theparacentral and/or peripheral Fresnel portion has radially discontinuouspower addition and/or subtraction to further extend the depth of field(or focus) in a manner similar to that of a typical bifocal or trifocalor extended depth of focus contact lens.

In still another embodiment, for both the continuous and discontinuouslens surface profile cases, the relative refractive power increasescontinuously or discontinuously from the central zone to the paracentralzone as well as within the paracentral zone and then further increasescontinuously or discontinuously from the paracentral zone to theperipheral zone and/or within the peripheral zone. In such a case,compared to the net refractive power of the central zone that correctsthe refractive error(s) of a myopic eye, the paracentral zone of theIRODR spectacle will form myopically defocused image of distant orintermediate paracentral object on the paracentral retina that is mosteffective in terms of myopic progression control, and the peripheralregion of the IRODR spectacle will bend peripheral light rays withstronger light bending power to expand the field of view.

In still another embodiment, for both the continuous and discontinuouslens surface profile cases, the relative refractive power increasescontinuously or discontinuously from the central zone to the paracentralzone as well as within the central zone and then decreases continuouslyor discontinuously from the paracentral zone outer edge to the outeredge of the peripheral zone. In such a case, compared to the netrefractive power of the central zone that corrects the refractiveerror(s) of a myopic eye, the paracentral region of the IRODR spectaclewill form myopically defocused image of distant or intermediateparacentral object on the paracentral retina that is most effective interms of myopic progression control, and the peripheral region of theIRODR spectacle will gradually lessen the effect of optical minimizationand will transition to normal vision near the edge of the peripheralregion.

Still another aspect of the present invention is to make the IRODRcombination have astigmatism correction capability. The astigmatismcorrection means can be made on any one of the optical interfaces andpreferably, the astigmatism correction means is implemented by shapingone or both of the outer two relatively flatter surfaces so fabricationof the two inner surfaces can be more standardized to save cost.

Still another aspect of the present invention is to make the IRODRcombination also have high order aberration correction capability.Modification of the net refractive power over the whole area of thespectacle lens can be made with freeform optics to not only correctcentral refractive errors (including astigmatism) but also compensateother higher order aberrations in order to form an ideal image shellwith sharp focus of distant or intermediate object on the fovea ormacula and ideal myopic defocus in the desired paracentral and/orperipheral retinal area to maximize the myopia progression control orprevention effect. For example, one ideal myopic defocus in the desiredparacentral and/or peripheral retinal area is to make the sagittal imageshell sharply focused on the paracentral and/or peripheral retinal area.

Still another aspect of the present invention is to design a near visionregion on the lower portion of the IRODR spectacle and a distant orintermediate vision region on the central and upper portion of the IRODRspectacle in a similar fashion as a standard bifocal spectacle lens or aprogressive addition spectacle lens offers, where again any one or moreof the optical interfaces can be shaped appropriately to achieve thegoal.

In one embodiment, the discontinuity in refractive power transitionbetween the lower portion and the central/upper portion of the spectacleis made on one or both of the two inner lens surfaces so the step is notfelt on one or both of the two outer surfaces. In another embodiment,the lower near vision portion has a different optical minimizationpercentage than that of the upper distance vision portion.

Still another aspect of the present invention is to design a near visionregion on the lower portion of the IRODR combination and a distantvision region on the central/upper portion of the IRODR combination witha progressive add power transition in a similar manner as a standardprogressive addition spectacle lens offers, where again any of theoptical interfaces can be shaped appropriately to realize the design.

Still another aspect of the present invention is to design the IRODRspectacle such that it deliberately creates a certain degree of tunnelvision with image from a large field of view in the object space formed(with a certain degree of paracentral and/or peripheral myopic defocusfor the case of myopia progression control) only within a desiredcentral portion of the retina that is most effective in controllingmyopia progression. This can be achieved by making the peripheral regionof the IRODR spectacle having a stronger net negative refracting orprismatic power to bend peripheral light rays towards the paracentralregion of the retina.

In one embodiment, the tunnel vision effect is created with a black tubesection that mechanically holds the two refractive elements of the IRODRspectacle together. In another embodiment, the tunnel vision effect iscreated by forming a black peripheral or annular ring or race track onany one or more of the optical interfaces of the two refractiveelements. In still another embodiment, the tunnel vision effect creationannular ring or race track is formed with apodization or gradualtransparent-to-opaque-transition or gradualtransparent-to-opaque-to-transparent transition. In still anotherembodiment, the object field of view is further enlarged by designingthe refractive element(s) panoramically curved.

These and other features and advantages of the present invention willbecome more readily apparent to those skilled in the art upon review ofthe following detailed description of the preferred embodiments taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the present invention may be more clearly ascertained,some embodiments will now be described, by way of example, withreference to the accompanying drawings, in which:

FIG. 1A shows what happens to the sharp focus image positions relativeto the retina of a young emmetropic eye when the eye is fixating onobject P and when different objects from the surrounding opticalenvironment are imaged by the emmetropic eye onto its retina;

FIG. 1B shows what happens to the sharp focus image positions relativeto the retina of a young myopic eye that is wearing a single elementvision correction spectacle lens when the eye is fixating on object Pand when different objects from the surrounding optical environment areimaged by the myopic eye with conventional vision correction. Object Frepresents the frame of the spectacle;

FIG. 1C shows what happens to the sharp focus image positions relativeto the retina of a young myopic eye that is wearing a multi-focalcontact lens when the eye is fixating on object P and when differentobjects from the surrounding optical environment are imaged by themyopic eye with the multi-focal contact lens correcting myopia and atthe same time extending the depth of focus by creating multiple imagesof the same object at different focus through dividing the contact lensinto different focusing zones;

FIG. 2A shows a conventional reverse Galilean telescope placed in frontof an eye when a distant object is optically relayed to an emmetropicpresbyopic eye in which case the retinal image of the object will landon the retina. The positive eyepiece lens has a front focal point thatoverlaps with the front focal point of the negative lens;

FIG. 2B shows a conventional reverse Galilean telescope placed in frontof an eye when a near object is optically relayed to an emmetropicpresbyopic eye in which case the retinal image of the object will landbehind the retina. The positive eyepiece lens has a front focal pointthat overlaps with the front focal point of the negative lens;

FIG. 3A illustrates a wearable Increased Resolvable Object DistanceRange (IRODR) optical device in accordance with one embodiment of thepresent invention;

FIG. 3B shows what happens to the image positions relative to the retinaof a young person's eye wearing an embodiment of the present inventionwhen the eye is fixating on object P. The net effect of the IRODR lenscombination is to optically push nearby objects further away from theeye and meanwhile, if the young eye is myopic the IRODR lens combinationcan also optically bring a faraway object closer to the eye as a singleelement vision correction lens does;

FIG. 3C shows one embodiment of the presently disclosed IRODR spectacle.A negative lens with its central zone having a strong refractive poweris combined with a positive lens with its central zone having a somewhatless strong but positive refractive power where the front focal point ofthe central zone of the positive lens does not necessarily overlap withthe front focal point of the central zone of the negative lens;

FIG. 4A shows the ray tracing method being used to find out the imageposition and image size formed by the negative lens of an object placedat a relatively near object distance from the negative lens;

FIG. 4B shows the ray-trace diagram in finding out the final imageposition and size formed by the positive lens of the object formed as avirtual image by the negative lens but as the object for the positivelens;

FIG. 5 shows the merging together of FIG. 3 and FIG. 4, illustratingthat for a relatively close object, the final image position formed bythe combination of the negative lens and the positive lens is positionedfurther away from the combination as compared to the original objectposition;

FIG. 6 shows the ray-trace diagram in finding the final image positionand image size of an object that is closer to but still outside thefront focal point of the positive lens which is outside the front focalpoint of the negative lens;

FIG. 7 shows a plot of the relative distance difference between thefinal virtual image and the original object as a function of the objectdistance over a distance range from 100 mm to 10000 mm or from 0.1 m to10 m for a 30 mm focal length negative lens and a 40 mm focal lengthpositive lens with a lens separation distance of 9.8 mm;

FIG. 8 shows the relative percentage of position difference between thefinal virtual image and the original object normalized to the originalobject distance, i.e.

$\frac{\left\lbrack {\left( {{q_{2}} - d} \right) - p_{1}} \right\rbrack}{p_{1}},$

as a function of the original object distance p1 over an object distancerange from 100 mm to 10000 mm or from 0.1 m to 10 m;

FIG. 9 shows the plot of the overall optical magnification as functionof the object distance over an object distance range from 100 mm to10000 mm or from 0.1 m to 10 m;

FIG. 10 shows how the patient eye pupil is treated as an object and isimaged by the IRODR lens combination in the reverse direction to appearas a smaller pupil;

FIG. 11 shows how the presently disclosed IRODR lens combination can beadjusted to provide myopia correction. With a decrease in the separationdistance between the negative and the positive lens, the position of thefinal virtual image is brought closer. In addition, it also shows acomparison between the presently disclosed IRODR lens combination (solidcurve) and a single element negative lens (dashed curve) in terms of therelative percentage of position difference between the final image andthe original object normalized by object distance as a function of theobject distance over an object distance range from 100 mm to 10000 mm orfrom 0.1 m to 10 m when an object at 10 meter is imaged to 1 meter;

FIG. 12A shows one embodiment of the presently disclosed IRODR spectaclein which the paracentral and peripheral zone are designed to provideoverall net positive spherical aberration;

FIG. 12B shows an embodiment in which in addition to the aspheric designof the back surface of the negative lens, the front surface of secondthe positive lens also has an aspheric design;

FIG. 12C shows a comparison of the sharp focus image positions of someoptical environment objects as they land on the retina. The case of aneye wearing an IRODR spectacle lens combination is shown in the upperportion, whereas the case of the same eye wearing a conventional singleelement vision correction spectacle lens is shown in the lower portion;

FIG. 13 shows an embodiment in which the peripheral zone of the negativelens has a prism structure like an annular negative axicon lens that cancontrol or expand the field of view;

FIG. 14 shows an embodiment in which the central and paracentral zone ofthe IRODR lens combination does not induce spherical aberration while inthe peripheral zone the net refractive power of the combinationgradually reduces to a value as that of a conventional single elementprescription lens would have for the treatment of myopia;

FIG. 15 shows another embodiment in which the relative refractive powerhas a net add power in the paracentral zone relative to the central zoneand then a net decreasing power in the peripheral zone relative to theparacentral zone. These can be achieved by changing either the surfaceprofiles of the negative lens or the surface profiles of the positivelens or the surfaces profiles of both the negative lens and the positivelens;

FIG. 16A shows another embodiment in which the peripheral zone of thenegative lens is made with a Fresnel lens design so the overallthickness of the negative lens is reduced while the same goal to allowthe peripheral portion of the retina to sense the presence of anyperipheral object, especially the movement of peripheral object isachieved;

FIG. 16B shows an embodiment in which the peripheral zones of both thenegative lens and the positive lens are all made with Fresnel lensdesigns so the overall thickness of the IRODR lens combination can befurther reduced;

FIG. 16C shows an embodiment in which both the paracentral and theperipheral zones of both the negative lens and the positive lens are allmade with Fresnel lens designs so the overall thickness of the IRODRlens combination can be even further reduced;

FIG. 17 shows an embodiment where a pair of presently disclosed IRODRcombination is mounted on a frame as a spectacle;

FIG. 18 shows an embodiment in which a thicker opaque band isdeliberately created by making lens mounting frame section thicker suchthat the field of view border as seen through the IRODR combination isjust connected to the field of view outside the lens mounting frame;

FIG. 19 shows an embodiment where there is a net overall addition ofpositive refraction power in a lower portion of the IRODR combinationrelative to that in the center and upper portion of the IRODR spectacle;

FIG. 20 shows an embodiment in which solar cells and light sensors areembedded in the frame of the IRODR spectacle together with electronicsand firmware (not shown) to determine if a patient wearing the spectacleis indoor or outdoor and hence to keep or actuate a change in theseparation between the two refractive elements;

FIG. 21 shows one embodiment in which one relatively thick opticalmedium is shaped such that its front surface is strongly concavelycurved to function as a negative refracting element and its back surfaceis strongly convexly curved to function as a positive refractingelement; and

FIG. 22 shows one embodiment in which three optical interfaces areemployed to achieve the same goal with the intermediate opticalinterface serving the function to provide chromatic and sphericalaberration correction.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments of theinvention. Examples of these embodiments are illustrated in theaccompanying drawings. While the invention will be described inconjunction with these embodiments, it will be understood that it is notintended to limit the invention to any embodiment. On the contrary, itis intended to cover alternatives, modifications, and equivalents as maybe included within the spirit and scope of the invention. In thefollowing description, numerous specific details are set forth in orderto provide a thorough understanding of the various embodiments. However,the present invention may be practiced without some or all of thesespecific details. In other instances, well known process operations havenot been described in detail in order not to unnecessarily obscure norapply limitations to the present invention. Further, each appearance ofthe phrase “embodiment” at various places in the specification does notnecessarily refer to the same example embodiment.

Aspects, features and advantages of exemplary embodiments of the presentinvention will become better understood with regard to the followingdescription in connection with the accompanying drawing(s). It should beapparent to those skilled in the art that the described embodiments ofthe present invention provided herein are illustrative only and notlimiting, having been presented by way of example only. All featuresdisclosed in this description may be replaced by alternative featuresserving the same or similar purpose, unless expressly stated otherwise.Therefore, numerous other embodiments of the modifications thereof arecontemplated as falling within the scope of the present invention asdefined herein and equivalents thereto. Hence, use of absolute and/orsequential terms, such as, for example, “always,” “will,” “will not,”“shall,” “shall not,” “must,” “must not,” “first,” “initially,” “next,”“subsequently,” “before,” “after,” “lastly,” and “finally,” are notmeant to limit the scope of the present invention as the embodimentsdisclosed herein are merely exemplary.

FIG. 1A shows what happens to the sharp focus image positions relativeto the retina of a young myopic eye 104 when different objects (M, P, Qas central objects and X, Y, Z as peripheral objects) from thesurrounding optical environment are imaged by the eye 104 onto itsretina. The eye 104 is assumed to fixate on a central object P. In thiscase, central object M which is further away from central object P willform its image M in front of the central retina at a relatively largerdistance and central object Q which is closer than central object P fromthe eye 104 will form its image Q behind the retina at a relativelylarger distance.

At the same time, paracentral and/or peripheral objects will also casttheir images relative to the retina. If the distance of paracentraland/or peripheral object from the eye 104 X is about the same as that ofcentral object M, paracentral and/or peripheral object X will form itsimage X in front of the paracentral and/or peripheral retina also at arelatively large distance as in the case of object M. Paracentral and/orperipheral object Y, which is at an object distance approximately asthat of object P as indicated by the dashed line 160, will cast itsimage Y near the paracentral and/or peripheral retina. Paracentraland/or peripheral object Z, which is closer to the eye as central objectQ, will cast its image Z behind the paracentral and/or peripheral retinaalso at a relatively large distance.

Those behind the retina paracentral and/or peripheral images are said tobe hyperopically defocused on the paracentral and/or peripheral retina.Some clinical studies have shown that accommodation and hyperopicallydefocused paracentral and/or peripheral retinal images can both producesignals to cause the eye to elongate.

However, in an outdoor environment, paracentral and/or peripheralobjects are generally still quite some distance from a person's eye sothe need for accommodation is much less than indoor case and also thedegree of hyperopic defocus on the corresponding paracentral and/orperipheral retina is also lower in indoor case, i.e. their retinalimages are only slightly behind the paracentral and/or peripheral retinaso the signal to cause the eye to elongate is weak.

FIG. 1B shows what happens to the sharp focus image positions relativeto the retina of a young myopic eye 104 that is wearing a single elementvision correction spectacle lens 180 when the eye is fixating on centralobject P and when different objects (M, P, Q as central objects and X,Y, Z as peripheral objects) from surrounding optical environment areimaged by the myopic eye 104 with conventional vision correction ontoits retina. On the optical axis of the myopic eye 104 with conventionalvision correction, the eye is fixating on an intermediate central objectP. In this case, central object M, which is further away from centralobject P, will form its image M in front of the retina at a relativelylarger distance, and central object Q, which is closer than centralobject P from the eye 104, will form its image behind the retina at arelatively larger distance.

At the same time, paracentral and/or peripheral objects will also casttheir images relative to the retina. If the distance of paracentraland/or peripheral object X is about the same as that of the centralobject M, an image of object X will form in front of the paracentraland/or peripheral retina also at a relatively large distance as in thecase of object M. Object Y, which is at an object distance as that ofobject P as indicated by the dashed line 160, will cast its image Y onthe paracentral and/or peripheral retina. Object Z, which is closer tothe eye as object Q does, will cast its image Z behind the paracentraland/or peripheral retina also at a relatively large distance.

Note that in this case, the eye wire or rim of the spectacle frame, aperipheral object F, will be much closer to the eye than all other shownobjects (M,P,Q and X,Y,Z), so its retinal image F will be even furtherbehind the peripheral retina.

FIG. 1C shows what happens to the sharp focus image positions relativeto the retina of a young myopic eye 104 that is wearing a multi-focalcontact lens 190 when the eye 104 is fixating on central object P andwhen different objects (central objects M,P,Q and paracentral and/orperipheral objects X,Y,Z) from the surrounding optical environment areimaged by the young myopic eye 104 onto its retina. The design of atypical multi-focal contact lens 190 is that it is divided intodifferent concentric circular and/or annular ring zones with each zonehaving a different focusing power. As a result, one object after beingimaged onto the retina by the contact lens 190 and the wearer's eye 104will form multiple images (typical two or three) at different locationsrelative to the retina. Each zone can be designed to correct thewearer's refractive errors for either a far or a near object.

In this case, we assumed that for each object, two retinal images willbe formed. So for a central object P, there are two retina images P andP′ formed near the central retina. For central object M which is furtheraway than central object P, it will also form two retinal images M andM′ with both in front of the central retina at a relatively largedistance. Similarly, for central object Q, which is closer to the eyethan object P, it will form two retinal images Q and Q′ behind theretina at a relatively large distance.

As for the paracentral and/or peripheral objects X, Y and Z, each willalso form two retinal images, with X and X′ in front of the paracentraland/or peripheral retina at a relatively large distance, with P and P′near the paracentral and/or peripheral retina, and with Q and Q′ behindthe paracentral and/or peripheral retina at a relatively large distance.

FIG. 2A shows a conventional reverse Galilean telescope 202 placed infront of an eye 204. It is essentially an afocal Galilean telescopeturned backwards to reduce the size of a distant object image ratherthan enlarge it. The positive eyepiece lens 208 has a focal lengthmagnitude of B and its front focal point FB overlaps with the frontfocal point FA of the negative lens 206 having a focal length magnitudeof A. The positive lens 208 re-collimates light rays coming from thevirtual image point formed by the negative lens 206 at its front focalpoint in front of the positive eyepiece lens 208 and allows the eye 204to focus at infinity. The optical magnification is equal to the ratio offocal length magnitude of the negative lens 206 and that of the positivelens 208, i.e. A/B, and since A is less than B so there is opticaldemagnification or minimization. Such a design has been used as viewerfinder for cameras for a long time (see for example U.S. Pat. No.5,483,381).

Note that if the object light rays are not coming from a distanceobject, but from a nearby object as shown in FIG. 2B, they will bedivergent after passing through the lens combination 202 comprising thenegative lens 206 and the positive lens 208, and as a result, form animage behind the retina of an emmetropic eye 204, resulting in hyperopicdefocus on the retina for an eye that does not have accommodationcapability, such as an emmetropic presbyopic eye 204.

In accordance with the present invention, FIG. 3A shows what happens tothe sharply focused image positions relative to the retina of a youngperson's eye 304 wearing an embodiment of an optical device 310, thatadvantageously increases the resolvable object distance range of severalobjects located at different distances along a visual angle distancethereby reducing focus accommodating demands especially when a user isvisually fixating on a nearby object. Optical device 310 can be used asa vision aid for a range of visual impairments including myopia andpresbyopia.

Referring now to FIG. 3B, the optical device 310 of FIG. 3A incorporatesmodified and rearranged lens elements from a reverse Galilean telescopeto create an Increased Resolvable Object Distance Range (IRODR) lenscombination 302 comprising a negative lens 306 and a positive lens 308.As will be described in more detail later, the net effect of the IRODRlens combination 302 is to optically push closer object further awayfrom the eye and meanwhile, if the young eye is myopic the IRODR lenscombination can also optically bring a faraway object closer to the eyeas a single element vision correction lens does. In other words, thepresent invention can optical increase the resolvable object distancerange, leading to an increase in the depth of field (or focus).

When different objects (M, P, Q as central objects and X, Y, Z asperipheral objects) from a surrounding optical environment are imaged bythe eye 304 wearing an IRODR lens combination 302, a different situationin comparison to FIG. 1A to FIG. 1C occurs for the retinal images.Assuming again that the eye 304 wearing the IRODR lens combination 302is fixating on a central object P, then the central object P will formits image P on the central retina. In this case, a central object Mwhich is further away from central object P will form its image M infront of the central retina but at a relatively shorter distance fromthe retina and a central object Q, which is closer than central object Pfrom the eye 304, will form its image Q behind the retina but also at arelatively shorter distance.

At the same time, paracentral and/or peripheral objects will also casttheir images relative to the retina. If the distance of paracentraland/or peripheral object X is about the same as that of the centralobject M, object X will form an image X in front of the paracentraland/or peripheral retina but at a shorter distance from the retina. Ifthe distance of paracentral and/or peripheral object Y is about the sameas that of the central object P as indicated by the dashed line 360,object Y will form an image Y on the paracentral and/or peripheralretina. If the distance of paracentral and/or peripheral object Z isabout the same as that of the central object Q, object Z will form animage Z behind the paracentral and/or peripheral retina but at a shorterdistance from the retina.

So with the present invention, the signals that could possibly cause theeye to elongate, including accommodation and hyperopic defocus on theparacentral and/or peripheral retina, will be weaker than that when thesame person is not wearing a lens or is wearing a single element visioncorrection lens or a multi-focus contact lens. To interpret this in adifferent way, if there is a range of retinal images that are relativelysharply focused near the retina such that to the eye, they are stillresolvable to produce signal to the eye so the eye treat them as infocus, then corresponding to this range, the present invention canincrease the range of objects in the object space that are stillresolvable as not blurred by the eye when compared with prior arts.

FIG. 3C shows one embodiment of the presently disclosed IRODR spectacle302 in which the central zone of the present disclosed IRODR spectacleis represented by a negative lens 306 and a positive lens 308. As willbe seen soon, the central zone of the design can substantially extendthe depth of field (or focus) while not having issues related to singleelement based contact lens designs that extend the depth of field (orfocus). This feature can directly be used to treat presbyopia and alsoacts as one of the several clinically proven approaches that caneffectively control myopia progression. We will later discuss theparacentral and/or peripheral design that will not only provide benefitsin terms of field of view control, but also function to provide featuresassociated with the other clinically proven myopia progression controlapproaches.

In FIG. 3C, a negative lens 306 with a strong negative refractive powerin its central zone is combined with a positive lens 308 having asomewhat less strong but positive refractive power in its central zone.The front focal point FB of the positive lens central zone does not needto overlap with the front focal point FA of the negative lens centralzone. In general for a myopic eye and an emmetropic presbyopic eye, theparaxial front focal point FB of the positive lens is arranged in frontof the paraxial front focal point FA of the negative lens. The strengthof the refractive power of the central zone of both the negative lens306 and the positive lens 308 is such that they can be arranged closeenough to realize a practical compact design of a spectacle while alsocorrecting the refractive error(s) of a patient eye 304. Preferably, thelens material used to make these two lenses is a lightweight highrefractive index polymer such as those with a refractive index of around1.74.

Such an arrangement can provide a number of features very desirable forpresbyopia treatment and myopia progression control as will be discussedbelow.

To understand the basic principle of operation and practicality of thedesign, we assume that the central zones of the two lenses can be, to afirst degree of approximation, treated as two thin lenses separated by adistance d. We can consider the image formed by the central zone of thenegative lens 306 as the object for the central zone of the positivelens 308. We will firstly use the ray tracing method to find out wherethe final image is formed if an object is placed at some intermediatedistance in front of the IRODR spectacle 302 outside the front focalpoint FB of the of the positive lens 308 which is outside the frontfocal point FA of the negative lens 306. We will then use the thin lensimage formation equations to do some numerical analysis to discuss thebasic properties of the presently disclosed IRODR spectacle for lightrays that propagate paraxially through the central portion of the twolenses and to illustrate why such a design is beneficial in terms ofpresbyopia treatment and myopia progression control.

FIG. 4A shows the ray tracing method being used to find out the imageposition and image size formed by a negative lens 306 of an object 412placed at an object distance of p1 from the negative lens 306. A lightray from a point on the top of an object traveling parallel to theoptical axis toward the negative lens 306 will refract divergently suchthat its backward extension passes through the front focal point FA onthe object side of the negative lens 306. A light ray from a point onthe top of an object 412 traveling to the exact center of the negativelens 306 will continue to travel in the same direction. The image point414 of the top of the object is the point where the backward extendedrefracted light ray intersects with the light ray that propagate throughthe center of the negative lens 306. Note that the image 414 is locatedinside the front focal point FA of the negative lens 306 with themagnitude of the image distance |q1| being less than the magnitude A offocal length of the negative lens 306.

FIG. 4B shows the ray tracing method being used to find the final imageposition 416 and image size formed by the positive lens 308 of thevirtual object 414 (formed by the negative lens 306 as the image 414 butas the virtual object 414 for the positive lens 308). Note that sincethe front focal point FB of the positive lens is outside the front focalpoint FA of the negative lens as shown in FIG. 3B, the virtual object414 as seen by the positive lens 308 (formed as the image 414 by thenegative lens 306) is therefore within the front focal point FB of thepositive lens 308 with p2 being less than the magnitude B of the focallength of the positive lens 308, where p2 represents the object distancerelative to the positive lens 308. In this case the light rays willdiverge after refracting through the positive lens 308. When refractedlight rays diverge, a virtual image is formed.

A ray from a point on the top of the virtual object 414 (i.e. image 414formed by the negative lens 306) traveling through the center of thepositive lens 308 will continue to travel in the same direction. A rayfrom a point on the top of the virtual object 414 (i.e. image 414 formedby the negative lens 306) traveling in a direction that appears as it isfrom the front focal point FB of the positive lens 308 will be refractedand proceed parallel to the optical axis upon exiting from the positivelens 308. When these two light rays emerge from the right side of thepositive lens 308 and are extended backward, they will intersect and thepoint of intersection is where the top of the final image 416 is. Wewill use |q2| to represent the magnitude of the final image distancerelative to the positive lens 308. As can be seen, an enlarged virtualimage 416 relative to the virtual object 414 of the positive lens 308 isformed.

When we combine the two diagrams of FIG. 4A and FIG. 4B as shown in FIG.5, we can see that in this particular case, the final image 416 formedby the IRODR combination 302 of the negative lens 306 and the positivelens 308 is further away from the original object 412. In theillustrated case, the final image 416 is smaller in size as compared tothe original object 412.

To find out what happens if the object is closer to but still outsidethe front focal point FB of the positive lens which is outside the frontfocal point FA of the negative lens, we have done ray tracing for such acase as shown in FIG. 6. It can be seen that in this particular case,the final image 616 is larger in size than the original object 612 butstill, the position of the final image 616 is further away from theoriginal object 612. Although with ray tracing, it is difficult todetermine the exact relative position of the intermediate image 614 andthe final image 616 with respect to the original object 612, one thingis obvious and that is, a nearby object 612 optically refracted by thepresently disclosed IRODR spectacle 302 will appear to be further awayfrom the eye 304 of a patient wearing such a spectacle.

In order to better understand the position and size of the final imagein comparison to those of the original object over a large objectdistance range, we can use the thin lens image formation equations.Assuming that light rays travel from left to right toward a thin lens,the thin lens equation is

${\frac{1}{p} + \frac{1}{q}} = \frac{1}{f}$

wherein

p is the object distance (from object to thin lens), is positive for areal object located to the left of the lens, and is negative for avirtual object located to the right of the thin lens,

q is the image distance (from image to thin lens), is positive for areal image formed to the right of the lens, and is negative for avirtual image formed to the left of the thin lens,

f is the focal length (from either front or back focal point to thinlens), is positive for a converging lens and negative for a diverginglens.

The optical magnification m produced by a thin lens is given by

$m = {- \frac{q}{p}}$

If the magnification is negative then the image will be upside-downcompared to the object. If the magnification is positive then the imagewill have the same orientation as the object.

Again, we consider the image formed by the negative lens as the objectfor the positive lens. Given that the first lens is a negative lens, wehave f1=−A where A (with a positive value) is the magnitude of the frontfocal length of the negative lens. Therefore,

${\frac{1}{p_{1}} + \frac{1}{q_{1}}} = {\frac{1}{f_{1}} = {- \frac{1}{A}}}$or$q_{1} = {{- \frac{1}{\left( {\frac{1}{A} + \frac{1}{p_{1}}} \right)}} = {- \frac{p_{1}*A}{\left( {p_{1} + A} \right)}}}$

Because our object is real and on the left side of the negative lens, p1is positive. From the above equation and the fact that A is positive, q1is therefore negative and the absolute value of q1 is

${q_{1}} = \frac{p_{1}*A}{\left( {p_{1} + A} \right)}$

This means that the first image formed by the negative lens is on theleft side of the negative lens, and is a virtual image. Since

${\frac{p_{1}}{\left( {p_{1} + A} \right)} < 1},$

and theretore, |q₁|<A, this first virtual image is hence within thefront focal point FA of the negative lens.

Also since the object is outside the front focal point FB of thepositive lens which is outside the front focal point FA of the negativelens, we have |q₁|<A<p₁. As q1 is negative, the first opticalmagnification associated with the negative lens is

${m_{1} = {{- \frac{q_{1}}{p_{1}}} = \frac{q_{1}}{p_{1\;}}}},$

which is positive and less than one, meaning that the first image isupright and minimized relative to the object.

We can now treat this virtual image as the object of the positive lensand find out where the final image formed by the positive lens is. Notethat the object distance to the positive lens is positive and is

p₂ = q₁ + d

where d is the separation distance between the negative lens and thepositive lens, assuming both can be treated as thin lenses. Applying thethin lens image formation equation to the positive lens, we have

${\frac{1}{p_{2}} + \frac{1}{q_{2}}} = {\frac{1}{f_{2}} = \frac{1}{B}}$Or$q_{2} = {\frac{1}{\left( {\frac{1}{B} - \frac{1}{p_{2}}} \right)} = \frac{p_{2}*B}{p_{2} - B}}$

Our design is that the front focal point of the positive lens is outsidethe front focal point of the negative lens. Given the fact that thevirtual image formed by the negative lens (which now acts as the objectof the positive lens) is within the front focal point of the negativelens (which is within the front focal point of the positive lens), wecan conclude that p₂=|q₁|+d is less than B, so q2 is negative.Therefore, the absolute value of q2 is

${q_{2}} = \frac{p_{2}*B}{B - p_{2}}$

Meanwhile, since B>|B−p₂|, |q₂| is thus greater than p₂. Therefore, thesecond optical magnification associated with the positive lens,

${m_{2} = {{- \frac{q_{2}}{p_{2\mspace{11mu}}}} = \frac{q_{2}}{p_{2}}}},$

is positive and greater than one. This means that final image formed bythe positive lens is on the left side, is an upright virtual image, andis magnified relative to the intermediate image formed by the negativelens.

The relationship between the final virtual image distance referenced tothe negative lens (|q2|−d) and the original objective distance p1 alsoreferenced to the negative lens, is

$\left\lbrack \left( {{q_{2}} - d} \right) \right\rbrack = {\left\lbrack \left( {\frac{p_{2}*B}{B - p_{2}} - d} \right) \right\rbrack = \frac{{p_{1}\left( {{AB} + {Ad} + d^{2}} \right)} + {Ad}^{2}}{{p_{1}\left\lbrack {B - \left( {A + d} \right)} \right\rbrack} + {A\left( {B - d} \right)}}}$

Note that to determine if the final image is formed further away orcloser relative to the original object, we need to compare the value of(|q2|−d) with the value of p1. The difference [(|q2|−d)−p1] can beexpressed as

$\left\lbrack {\left( {{q_{2}} - d} \right) - p_{1}} \right\rbrack = {\left\lbrack {\left( {\frac{p_{2}*B}{B - p_{2}} - d} \right) - p_{1}} \right\rbrack = {\frac{{p_{1}\left( {{AB} + {Ad} + d^{2}} \right)} + {Ad}^{2}}{{p_{1}\left\lbrack {B - \left( {A + d} \right)} \right\rbrack} + {A\left( {B - d} \right)}} - p_{1}}}$

As a practical example, we can choose the magnitude of the focal lengthof the negative lens to be A=30 mm, the magnitude of the focal length ofthe positive lens to be B=40 mm, and the separation distance between thetwo lenses to be d=9.8 mm. With such a selection of the two lenses andthe arrangement, basically all practical nearby objects, like a computerscreen and a cell phone screen held by a person, will generally beoutside the positive front focal point FB.

FIG. 7 shows a plot of the relative distance difference between thefinal virtual image and the original object, [(|q2|−d)−p1], as afunction of the object distance p1 over an object distance range from100 mm to 10000 mm or from 0.1 m to 10 m. It can be seen from FIG. 7that the relative distance difference is positive for objects relativelyclose to the IRODR spectacle and negative for objects relatively distantto the IRODR spectacle. This means that nearby objects will be opticallypushed further away from the IRODR spectacle and distant objects will beoptically brought closer to the IRODR spectacle.

To better illustrate the relative change in distance, it is moreinformative to show the relative percentage in terms of the distancedifference between the final image and the original object normalized tothe original object distance and this percentage can be expressed as

$\frac{\left\lbrack {\left( {{q_{2}} - d} \right) - p_{1}} \right\rbrack}{p_{1}} = {\frac{\left\lbrack {\left( {\frac{p_{2}*B}{B - p_{2}} - d} \right) - p_{1}} \right\rbrack}{p_{1}} = {\frac{\left( {{AB} + {Ad} + d^{2}} \right) + \frac{{Ad}^{2}}{p_{1}}}{\left\lbrack {B - \left( {A + d} \right)} \right\rbrack + \frac{A\left( {B - d} \right)}{p_{1}}} - 1}}$

FIG. 8 shows a plot of the relative percentage in position differencebetween the final virtual image and the original object normalized tothe original object distance as a function of the original objectdistance over an object distance range from 100 mm to 10000 mm or from0.1 m to 10 m.

It can be seen from FIG. 8 that for a very nearby object that is about100 mm or 4 inches away from the IRODR spectacle, the image is pushedabout 75% away from the original object position. FIG. 7 and FIG. 8 tellus that with the use of the IRODR spectacle, an object originally at 100mm or 4 inches away will appear to come from a distance of about 175 mmor about 7 inches. As the object distance from IRODR spectacleincreases, the relative pushed-away distance percentage drops. For anobject at about 1 meter, its image is pushed outward by about 44%, so itappears to come from a distance of about 1.44 meters. More interestingis the fact that as the object distance further increases, the relativepushed-away distance percentage continues to drop until at a certaindistance (3.4 meter in the current case), it drops to zero percentage.This means that for an object at 3.4 meters, its virtual image is alsoat 3.4 meters. More importantly, as the object distance furtherincreases, the relative pushed-away distance percentage continues todrop below zero. A negative percentage means the final virtual image iscloser than the original object. At an object distance of 10 meter, therelative percentage is −45% which means that the image is about 5.5meters away from the IRODR spectacle.

At this moment, one may wonder what the overall optical magnification isover such an object distance range. To determine if the final virtualimage is magnified or de-magnified relative to the original object, weneed to find the overall optical magnification which is

${m - {m_{1}*m_{2}}} = {{\left( {- \; \frac{q_{1}}{p_{1}}} \right)*\left( {- \frac{q_{2}}{p_{2}}} \right)} = \frac{A*B}{{\left( {p_{1} + A} \right)*\left( {B - d} \right)} - {p_{1}*A}}}$

FIG. 9 shows the plot of the overall optical magnification as a functionof the object distance over an object distance range from 100 mm to10000 mm or from 0.1 m to 10 m. From FIG. 9, it can be seen that forvery nearby object, there is an optical magnification greater than one,meaning that while a very near object is pushed away by the IRODRspectacle, the final virtual image is somewhat enlarged. At an objectdistance of around 1.4 meters, the final virtual image and the originalobject has approximately the same size. As the object distance furtherincreases, the overall optical magnification drops below 100%, meaningthe final virtual image will appear smaller than the original object.

By comparing FIG. 7, FIG. 8 and FIG. 9, it can be seen that for nearbyobjects like a cell phone screen with an object distance from about 100mm or 4 inches to about 1000 mm or 3 feet, the present example can pushthe object away as a virtual image by a relative percentage from about75% to about 44% while the virtual image would appear bigger than theoriginal object. At an intermediate distance of around 3.5 meters, thevirtual image will appear at about the same distance away as the realobject does. In addition, at 3.5 meters where the image distance isequal to the original object distance, the size of the image is about75% that of the original object which is equal to the ratio of A/B. Fora distant object, the virtual image will appear quite closer to the eye(10 meter object appears to be 5.5 meter away) while the size of thevirtual image is about half the size of the object. Given the fact thatthe distance is also reduced by about 50%, the net effect is that thevisual angle or object field angle between the final virtual image andthe original object is about the same. This means that a distant objectimaged through the IRODR spectacle will appear approximately equally asresolvable as it would be without the IRODR spectacle.

It should now be clear that the presently disclosed IRODR spectacle canincrease the depth of field (or focus) by pushing nearby object furtheraway and bringing distant object closer. With this embodiment, if aslightly myopic presbyopic eye is originally able to resolve an objectwithin an object distance range from 0.5 to 5 meter, then with the IRODRspectacle, the same person will be able to resolve object within anobject distance range from 0.3 to 7.7 meter. The IRODR spectacleeffectively functions as an extended-depth-of-field (or focus) devicewithout the effect of contrast reduction and blurred background ghostimages as some typical bi-focal or tri-focal or extended-depth-of-field(or focus) contact lenses would produce because these contact lenses aretypically made with multiple concentric Fresnel zone type of rings toproduce multiple focused images of an object at different imagedistances relative to the retina.

Another benefit of the presently disclosed IRODR spectacle is that itcan effectively reduce the pupil size of the patient eye and thereforeeven further increase the depth of field (or focus) in addition to whathas been discussed above, a property desirable for both presbyopiatreatment as well as myopia progression control.

To see how this effective pupil size reduction is realized, we can referto FIG. 10 which treats the patient eye pupil as an object with the twoinward pointing arrows as shown in FIG. 10 representing the eye pupil.The light path is turned backward, i.e., the thin lens formula appliesnow to light rays travelling from right to left. In practice, the objectwhich in this case is the pupil imaged by the cornea as represented by1042 is positioned at a distance of about p3=12 mm from the positivelens 308, where p3=12 mm is a typical cornea apex to spectacle lensdistance. Given that the central zone of the positive lens 308 can beapproximated as a thin lens with a focal length magnitude of fB=B=40 mm,the object 1042 is therefore way inside the focal length of the positivelens 308. As such the image 1044 formed by the positive lens 308 will bea magnified virtual image with a negative image distance of q3=−|q3|.Using the principle that a parallel light ray from the edge of the pupilwill be refracted by the positive lens 308 to travel towards its focalpoint on the other side (in this case the side further away from theeye) and the light ray that travels to the center of the positive lens308 will propagate along the same direction, we can backward extend therefracted light rays to find the intersection point and hence to findthe first image 1044.

Using the thin lens equation (now with light ray travels from right toleft)

${\frac{1}{p_{3}} + \frac{1}{q_{3}}} = {\frac{1}{f_{B}} = \frac{1}{B}}$

we can find the value of q3 which is given by

$q_{3} = {\frac{1}{\left( {\frac{1}{B} - \frac{1}{p_{3}}} \right)} = {\frac{p_{3}*B}{p_{3} - B} = {\frac{12\mspace{14mu} {mm}\;*\; 40\mspace{14mu} {mm}}{{12\mspace{14mu} {mm}} - {40\mspace{14mu} {mm}}} \cong \; {{- 17.14}\mspace{14mu} {mm}}}}}$

We can then treat this first virtual image 1044 as the object of thenegative lens 306 which has a focal length of fA=−A=−30 mm. Given theseparation distance between the positive lens 308 and the negative lens306 is d=9.8 mm, the object distance with respect to the negative lens306 is p4=|q3|+d=17.14 mm+9.8 mm=26.94 mm.

Again, using the thin lens equation

${\frac{1}{p_{4}} + \frac{1}{q_{4}}} = {\frac{1}{f_{A}} = {- \frac{1}{A}}}$

we can find the value of q4 which is given by

$q_{4} = {\frac{1}{\left( {\frac{1}{A} - \frac{1}{p_{4}}} \right)} = {{- \frac{p_{4}*A}{p_{4} - A}} = {{- \frac{26.94\mspace{14mu} {mm}\;*\; 30\mspace{14mu} {mm}}{{26.94\mspace{14mu} {mm}} + {30\mspace{14mu} {mm}}}} \cong \; {{- 14.19}\mspace{14mu} {mm}}}}}$

Therefore, the overall optical magnification is

$m^{\prime} = {{m_{3}*m_{4}} = {{\frac{q_{3}}{p_{3}}*\frac{q_{4}}{p_{4}}} = {{{\frac{- 17.14}{12}*\frac{- 14.19}{26.94}} \cong 0.75} = {75\%}}}}$

This means that if the pupil 1042 is originally 4 mm in diameter, to theworld outside the IRODR spectacle, the final image 1046 will beeffectively only 3 mm in diameter. Given the fact that the magnitude ofdepth of field varies inversely with pupil diameter, if we assume thatpupil diameter with or without a wearing a IRODR spectacle is the same,then the depth of field increase due to purely the pupil size effectwill be 1/0.75=1.33. In other words, if a slightly myopic presbyopic eyeis originally able to resolve object within an object distance rangefrom 0.5 to 5 meter, with the IRODR spectacle that does not include thepupil reduction effect, the same person will be able to resolve objectwithin an object distance range from 0.3 to 7.7 meter. The depth offield in this case is 7.7−0.3=7.4 meter. But with the pupil reductioneffect, the depth of field will be further increased to 7.4/0.75=9.87meter. Even if the nearby-still-resolvable object distance remains thesame, the person will be able to resolve object within an objectdistance range from 0.3 to 9.57 meter. In other words, the depth offield effectively doubled from the original 0.5 to 5 meters to about 0.3to 10 meters.

In addition to the advantages associated with the substantial increasein the depth of field which is obviously beneficial in treatingpresbyopia as well as in controlling myopia progression, anotheradvantage of the design (as an embodiment of the present disclosure) isthat by changing the separation distance between the negative lens andthe positive lens, within a certain limited range, a distant orintermediate object can be optically tuned to appear as coming from adesired distance and therefore the IRODR spectacle can be easily tunedto cater for different needs while maintaining the benefit of extendeddepth of field.

To illustrate this property, let us first take a look at how a singleelement negative lens can be used to treat myopia. A relaxed myopic eyewithout wearing a prescribed negative lens can only focus on an objectat some near distance range. The reason why a negative lens can treatmyopia is that the negative lens can optically bring a distant objectcloser to the eye by forming a virtual upright image at that neardistance range. However, when an object such as a computer screen or acell phone screen is no longer distant but nearby, the negative lenswill form a virtual image even closer to the eye. If the eye has noaccommodation capability like in the case of a myopic presbyopic eye,then the image formed by the eye will land behind the retina. In otherwords, there will be hyperopic defocus on the retina or the image on theretina will be a hyperopically blurred image. In such a case, thepresently disclosed IRODR spectacle with extended depth of field canobviously provide help in treating presbyopia.

For example, if a presbyopic eye is slightly myopic such that wearing anegative lens with a diopter value of 1.0 D will enable the patient tosee a distant object about 10 meters away clearly with best focus. Thiswould mean that without any spectacle, the patient can form on theretina a best focused image of an object at a distance of about 1.0meter away. One desired IRODR spectacle design, as one embodiment of thepresent disclosure, would be to optically relay an object at about p1=10meter away to appear as a virtual image at about |q2|=1.0 meter away.Using the equation that relates the final virtual image distance to theoriginal object distance as shown below

$\left\lbrack \left( {{q_{2}} - d} \right) \right\rbrack = {\left\lbrack \left( {\frac{p_{2}*B}{B - p_{2}} - d} \right) \right\rbrack = \frac{{p_{1}\left( {{AB} + {Ad} + d^{2}} \right)} + {Ad}^{2}}{{p_{1}\left\lbrack {B - \left( {A + d} \right)} \right\rbrack} + {A\left( {B - d} \right)}}}$

we can substitute p1=10 meter=10000 mm, |q2|=1 meter=1000 mm, A=30 mm,and B=40 mm into the above equation to find out the desired lensseparation distance d, i.e.

$\left\lbrack \left( {1000 - d} \right) \right\rbrack = \frac{{10000\left( {{30*40} + {30d} + d^{2}} \right)} + {30d^{2}}}{{10000\left\lbrack {40 - \left( {30 + d} \right)} \right\rbrack} + {30\left( {40 - d} \right)}}$

Solving for d, we have d≅8.57 mm. FIG. 11 shows such a special case inwhich with the separation distance d=8.57 mm, and the relationshipbetween the relative percentage of position difference between the finalvirtual image and the original object normalized to the original objectdistance

$\frac{\left\lbrack {\left( {{q_{2}} - d} \right) - p_{1}} \right\rbrack}{p_{1}},$

is plotted as a function of the original object distance p1 over anobject distance range from 100 mm to 10000 mm or from 0.1 m to 10 m. Insuch a case, very nearby object at a distance about 100 mm or 4 inchesfrom the IRODR spectacle will still be pushed further away by about 43%while a distant object at 10 meters away will be brought much closer by90% to a virtual image distance of about 1 meter.

As a comparison to the case of a single element prescription lens thatis also used to bring a 10 meter away object to one meter. We can usethe single element thin lens equation

${\frac{1}{p} + \frac{1}{q}} = \frac{1}{f}$

and substitute p=10000 mm, q=−1000 mm to obtain f≅−1111 mm. We can thenuse the relationship that

${q} = {\frac{p*{f}}{p - f} = \frac{1111p}{p + 1111}}$

to obtain the relationship between the relative percentage of theposition difference between the final virtual image and the originalobject normalized to the original object distance,

${\frac{\left\lbrack {{q} - p} \right\rbrack}{p} = {\frac{1111}{p + 1111} - 1}},$

as a function of the original object distance p over an object distancerange from 100 mm to 10000 mm or from 0.1 m to 10 m. In FIG. 11, thisrelationship is plotted as a dashed curve in order to compare with thecase of the presently disclosed IRODR lens combination.

As can be seen, for an object at 10 meters, both the single elementprescription lens and the presently disclosed IRODR lens combination canall bring the object 90% closer to the eye to make it appear as comingfrom 1 meter away. However, the single element negative lens will alsobring a nearby object further closer to the eye as the relativepercentage is always negative, whereas the presently disclosed IRODRlens combination will push a nearby object away from the eye becausewithin certain nearby object distance range, the relative percentage ispositive. More importantly, if the object is a nearby object such as acell phone held by a young child at a typical distance of about 200 mmor 8 inches, the presently disclosed IRODR lens combination can push theobject further away by about 30% to make it appear as coming from about260 mm or more than 10 inches, whereas in the case of the single elementmyopia correcting negative lens case, the object will be brought closerto the eye by about 15% to make it appear as coming from 170 mm orslightly less than 7 inches. This 90 mm or close to 4 inches virtualimage distance difference can mean a lot to myopia progression becausein the single element myopia correction negative lens case, the imageshell formed by the patient eye will much more likely to land behind theretina even if there is accommodation, whereas in the IRODR case,accommodation will much more likely make the image shell land on theretina.

In the IRODR case, if the standard myopic correction prescription lensis 2.0 Diopter, the calculated corresponding IRODR lens separationdistance will be d=7.16 mm. If the standard myopic prescription lens is3.0 Diopter, the calculated corresponding IRODR lens separation distancewill be d=5.87 mm. Note that these are very practical values becausealthough with thin lens assumption, the variation range of theseparation distance d can be from 10 mm to 0 mm, in practice, the lenswill have certain thickness which will limit the separation distancevariation range on the small value side.

This feature is beneficial in that it can enable a doctor to fine tunethe prescription at the time when a patient is testing a custom madeanti-myopia IRODR spectacle. Also if standard negative and positivelenses are made as a kit to cater for different myopic eyes, the totalnumber of discrete positive and negative lenses can be less. Forexample, the step in discrete lens refraction power selection can beevery 0.5 Diopter or even every 1.0 Diopter. In addition, the same lenspair can also be reused if there is a relatively small change in thespherical refractive error of a patient after wearing the IRODR lens forsome period of time. All these will substantially reduce the cost ascompared to standard single vision correction spectacles which aregenerally discarded after one to two years of use once there is myopicprogression.

Note also that the net effect of moving the negative lens closer to thepositive lens is to increase the separation distance between the frontfocal point of the positive lens relative to that of the negative lens,which will make the overall refraction of the combination having a netnegative refractive power, thus offering the capability to correct thespherical refractive error of a myopic eye.

On the other hand, if the eye is hyperopic, the positive lens can bemoved further away from the negative lens to make the front focal pointof the positive lens land behind the front focal point of the negativelens, which will make the overall refraction of the combination having anet positive refractive power, thus offering the capability to correctthe spherical refractive error of a hyperopic eye.

The above discussion clearly indicates that with the use of thepresently disclosed IRODR spectacle, by controlling the separationdistance between the negative lens and the positive lens, the same basicdesign that can increase the depth of field (or focus) substantially canalso be utilized to treat presbyopic myopia (or hyperopia) in additionto controlling myopia progression.

If the eye is not presbyopic as in the case of young children who haveaccommodation capability, then depending on the amplitude ofaccommodation, there will be an object distance range over which the eyecan still accommodate. Beyond that object distance range, the eye willno longer be able to accommodate. This limited accommodation range cancause accommodation lag.

One theory on why myopia progresses even when a negative prescriptionlens for best distance vision correction is worn by a myopic patient isthat with limited accommodation range, the patient wearing such aprescription lens will still not be able to fully bring a nearby objectlike a computer screen or a cell phone screen to sharp focus on theretina, meaning that the nearby object will be sharply focused behindthe retina even with maximum accommodation. This can send a signal tothe eye to cause its axial length to further elongate, resulting inmyopia progression.

Based on the above theory, many clinical trials have been conducted tocontrol or slow myopia progression using contact lenses that offerbi-focal or tri-focal or multi-focal or extended depth of focusproperties. These clinical trials seem to have proven that by correctingdistant refractive error and also at the same time extending the depthof field (or focus), myopia progression can indeed be controlled orslowed. Therefore, the presently disclosed IRODR spectacle has thepotential to treat myopia progression at a younger age before a child isable to easily and safely wear a contact lens while not having thoseundesirable effects associated with single element bi-focal or tri-focalor extended-depth-of-focus contact lenses such as blurred backgroundghost images.

It should be noted that instead of controlling the separation distancebetween the negative lens and the positive lens, another embodiment intreating myopia or control myopia progression is to either change thecentral zone refractive power of the positive lens or to change thecentral zone refractive power of the negative lens or to simultaneouslychange the central zone refractive power of the positive lens and thecentral zone refractive power of the negative lens. The ultimate goal isto optically relay a distant object to a desired distance at which arelaxed eye would, without wearing any spectacle lens, form a sharplyfocused image on the retina. Note that when the refractive power of thepositive lens is decreased (or increased), it is equivalent to say thatthe focal length magnitude of the positive lens is increased (ordecreased), which means that the front focal point of the positive lensis moved forward (or backward) relative to that of the negative lens.Similarly, when the refractive power of the negative lens is increased(or decreased), it is equivalent to say that the focal length magnitudeof the negative lens is decreased (or increased), which means that thefront focal point of the negative lens is moved backward (or forward)relative to that of the positive lens.

It should be noted that in the above analysis using either ray tracingdiagrams or thin lens image formation equations, we have treated thenegative lens and the positive lens as a thin lens and in practice theselenses are generally not very thin lenses so the analysis is only anapproximation. Therefore, there are differences between reality and theabove analysis. Although more accurate analysis can be done using, forexample, Zemax or other optical ray tracing or simulation software, wewould like to mention that with reduction to practice, we have builtprototypes that demonstrated performance that is generally in agreementwith the above analysis results.

So far, we have only discussed some embodiments related to the centralzone of the presently disclosed IRODR spectacle. Before we move on todiscuss embodiments related to the design of the paracentral andperipheral zones of the presently disclosed IRODR spectacle, we wouldlike to point out a few other features that can be associated the designof the central portion of the presently disclosed IRODR spectacle asvariations in terms of embodiments.

Firstly, in terms of the optical design of the central zone of thenegative lens and the positive lens, there can be many possible lensshape design options. For example, the negative lens can be bi-concave,or plano-concave, or negative meniscus and the positive lens can bebi-convex, plano convex and positive meniscus. Any possible combinationshould work. Although for better handling and cleaning of the IRODR lenscombination by the end user, it is preferable to have the less curvedsurface on the outside of the combination, the more curved side ofeither the negative lens or the positive lens can be either on the outerside or inner side. A preferred embodiment would be a negative meniscuslens in combination with a positive meniscus lens with the more curvedsurfaces of each of the two lenses arranged in between the two lenses sothe outer two surfaces are similar to those a conventional singleelement vision correction lens with less curvature.

Secondly, in terms of the practical refractive powers of the negativelens and the positive lens, given the fact that each lens, especiallythe negative lens with a relatively strong net refractive power, has acertain thickness even just for the central zone, the design ispreferably such that the overall thickness of the IRODR combination iswithin the range from 5 mm to 30 mm while the relative ratio of thefocal length magnitude of the positive lens over that of the negativelens FB/FA is preferably within the range from 125% to 175%, morepreferably on the 125% side.

To make this happen and also to ensure that there is significantextension in the depth of field (or focus) while the virtual image isnot de-magnified too much as compared to the original object size; therefractive power of the central zone of the negative lens is preferablyselected to have a focal length magnitude of 10 mm to 40 mm or anabsolute magnitude of refractive power between 25 Diopter to 100Diopter. Associated with this preferred refractive power magnitude rangeof the central zone of the negative lens, the focal length magnitude ofthe central zone of the positive lens is preferably from 12 mm (2 mmlonger relative to the 10 mm focal length magnitude of the negativelens) to 65 mm (25 mm longer relative to the 40 mm focal lengthmagnitude of the negative lens) or an absolute magnitude of refractivepower between about 15 Diopter to about 83 Diopter.

Thirdly, in terms of correcting the refractive errors of a patient eye,the design of the central zone of the two lenses can also include thecorrection of cylindrical refractive error or astigmatism in addition tospherical refractive error, or pure myopia and hyperopia. In oneembodiment, the IRODR combination is designed to have astigmatismcorrection feature made on any one of the optical interfaces.Preferably, the astigmatism correction means is implemented by shapingone or both of the outer two relatively less curved surfaces of theIRODR combination so the inner surfaces are dedicated to depth of field(or focus) extension and also spherical refractive error correction.This may make the manufacturing or fabrication of the lenses morestreamlined and more cost effective. In another embodiment, the outertwo surfaces both have astigmatism or cylinder power and the net overallastigmatism or cylinder power is tuned by rotating the two lenses. As aresult, the IRODR combination can realize both spherical and cylindricalrefractive power tuning with the separation distance dedicated tospherical refractive error correction tuning, and the orientation anglesof the two lenses dedicated to cylindrical refractive error correctiontuning.

Fourthly, in terms of correcting not only refractive errors of a patienteye but also higher order aberrations of the patient eye, the design ofthe central zone of the two lenses can also include the correction ofhigher order aberrations in addition to spherical refractive error (ormyopia and hyperopia) and cylindrical refractive error (or astigmatism).In one embodiment, the IRODR combination is designed to have astigmatismcorrection and higher order aberration correction features made on anyone of the optical interfaces. Preferably, the astigmatism correctionand higher order aberration correction means is implemented by shapingone or both of the outer two relatively less curved surfaces of theIRODR combination.

It should also be noted that the design of the central zone of thepresently disclosed IRODR spectacle should not be limited to sphericalsurface designs but should include other designs like aspherical designsand even freeform designs. In practice, aspherical designs might be morepreferred as this will result in less spherical aberration and also lessdistortions at least for the central vision. Also, the design of thenegative lens and the positive lens does not need to be limited tosinglet designs and either or both can be an achromatic doublet withchromatic and spherical aberration reduction taken into consideration ifneeded.

It is interesting to note that most of extended-depth-of-field (orfocus) designs for presbyopia treatment have been found to also offermyopia progression control effect. The link between myopia progressioncontrol and presbyopia treatment seems to relate to the fact that apresbyopia patient basically has no accommodation capability, whilereducing the degree of accommodation need or demand in the case of anemerging or low myopia patient reduces the chance that near object willform an image shell behind the retina due to accommodation lag orinsufficient accommodation capability to bring the image shell frombehind the retina to the retina.

So far, we have only discussed the central zone designs of the presentlydisclosed IRODR spectacle. As for the design of the paracentral andperipheral zones, they can affect other features related to the overalloptical effect of the IRODR spectacle that a patient can experience,such as distortion, overall field of view and the image shell positionrelative to the paracentral and peripheral retina. As will be discussedshortly, certain designs will benefit presbyopia treatment more whileother designs will benefit myopia progression control more.

Note that if the central zone designs are all spherical surface basedand are extended all the way from the center to the peripheral of theIRODR combination which is one embodiment of the present disclosure,such a spectacle will generally enable wide field of view capabilitywithin a central (and paracentral) retina area that the eye would coverwithout the IRODR spectacle. What this means is that if the eye hastunnel vision with only the central (and/or paracentral) portion of theretina responsive to incoming light, then by wearing such a IRODRspectacle, a wider field of view will be covered by the same central(and/or paracentral) retina area. This property to enable the central(and/or paracentral) retina area to view a wider field of view has notonly the benefit of optically relaying wider object field to within themost effective central and/or paracentral retina for most effectivemyopia progression control, but also the potential in assisting patientwith retinitis pigmentosa, glaucoma, and some AMD (Age-related MacularDegeneration).

Note also that while extending the depth of field (or focus) andsimultaneously correcting the refractive errors (or even higher orderaberrations) can address the key issue related to presbyopia as well asmyopia progression control to some extent, these central zone relatedapproaches have only explored some of several clinically proveneffective means that can control myopia progression. Using the presentlydisclosed IRODR spectacle with proper design of the paracentral and/orperipheral zone(s) of the spectacle, the other clinically proveneffective means can also be explored. So we will now move on to discussthe optical designs of those embodiments.

As is well known to those skilled in the art, when the eye becomes moremyopic, it becomes more prolate, thus the anterior-posterior lengthincreases without a change in the equator. This results in a morehyperopic periphery. Traditional vision correction lenses will correctthe central retina leaving the periphery more hyperopic, i.e., imageshell in the periphery is behind the retina. The amount of hyperopicdefocus increases when looking at nearby object during accommodation.

It has been clinically shown that the paracentral and/or peripheralretina has a greater influence than the central region of the retina orthe macula to blur and ocular growth. By reducing peripheral hyperopia,one can alter central refractive development and reduce the rate ofprogression of myopia. More interesting is the fact that peripheraladdition lenses designed to correct the distance centrally with aparacentral and/or peripheral add power can effectively slow myopiaprogression. The net effect of such a lens design will move the imageformed at the paracentral or peripheral retina forward, leaving theimage myopically defocused on the paracentral and/or peripheral retina,thus generating a visual stimulus to slow ocular growth.

As one embodiment of the presently disclosed IRODR spectacle, while thecentral zone of the IRODR combination is designed to fully correct fordistance or intermediate distance vision, the paracentral zone of theIRODR combination is designed with overall net add or plus powerrelative to that of the central zone to increase hyperopic correctionfrom the center moving outward in any direction to cover at least theparacentral zone. In other words, myopic defocus is induced in theparacentral retina. Note that what is meant by paracentral retina inthis disclosure is the retina area that has the most effect outside thecentral retina or fovea/macula in terms of controlling myopiaprogression or eye length growth. Typically when this paracentral retinaarea is transferred to the spectacle plane about 12 mm in front of thecornea apex in terms of light ray coverage area, it corresponds to anannular ring zone on the spectacle lens with an inner diameter of about10 mm and an outer diameter of about 20 mm.

FIG. 12A shows one embodiment of the presently disclosed IRODR spectaclewith a paracentral and peripheral zone design that is not something aconventional reverse Galilean telescope would have. In this embodiment,the negative lens 1206 has a plano or less curved front surface 1252while its back surface 1254 has a strongly concave aspherical surfacesuch that the paracentral and peripheral zone of the lens does notinduce negative spherical aberration. The positive lens 1208 a has aconvex spherical front surface 1256 a and a plano or less curvedspherical or spherical plus cylindrical back surface 1258. As a result,there is net positive spherical aberration over the whole lens area inaddition to refractive error correction prescription for the centralfovea or macula. This positive spherical aberration effectively meansthat paracentral and/or peripheral light rays that enter the eye pupiland land on the paracentral and/or peripheral retina will be focusedcloser to the ocular lens compared to central vision light rays. Inother words, this IRODR design will form image shell of distantparacentral and/or peripheral object in front of paracentral and/orperipheral retina and/or have effect in correcting paracentral and/orperipheral hyperopia.

Note that by making the outer most two surfaces plano or less curved,the two strongly curved surfaces are contained inside the IRODRcombination while the two outer surfaces are easier to handle and clean.With such a combination design, the IRODR spectacle will not onlycorrect the central refractive errors but also induce myopic defocus inthe paracentral (and/or, if needed, peripheral) retina, while, at thesame time, extend the depth of field (or focus). In other words, aparacentral (and, if needed, peripheral) image shell will be formed infront of paracentral (and/or peripheral) retina, thus creating myopicdefocus or myopic blur on paracentral (and/or peripheral) retina, whichis one of the other clinically proven effective means to slow or preventmyopia progression. In one embodiment, the aspheric design of the morestrongly curved back surface 1254 of the negative lens 1206 can becontrolled in such a manner that the net add power in the paracentral(and/or peripheral) zone of the overall IRODR combination is about 2 to3 Diopters and the addition of the power is gradual from the centralzone to the paracentral zone (and/or peripheral) in a similar way as astandard progression addition spectacle lens does but in all radialdirections. In addition, in the central zone, the aspheric design canalso, if needed, minimize or remove spherical aberration for the centralvision. Note that the design of the central zone does not need to berestricted to having a net positive spherical aberration. There are manyother designs that can induce myopic defocus on the paracentral and/orperipheral retina. For example, the same overall refraction effect canalso be achieved if the paracentral (and/or peripheral) zone of thefront surface of the positive lens is gradually more strongly curved toover compensate the negative spherical aberration induced by thenegative lens. In other words, as there are four optical interfaces thatcan be manipulated to control the overall refractive properties of theIRODR lens combination, there are many ways to design one or more ofthese surface profiles to achieve the same goal.

FIG. 12B shows an embodiment where in addition to the aspheric surfacedesign of the back surface 1254 of the negative lens 1206, the frontsurface 1256 b of second the positive lens 1208 b also has an asphericsurface design. In such a design, the asphericity of the back surface1254 of the negative lens 1206 and the asphericity of the front surface1256 b of the positive lens 1208 b can be controlled to graduallyproduce the desired add power in the paracentral zone while also togradually produce a transition of the overall net power from theparacentral zone to a desired value of the peripheral zone of theoverall IRODR combination.

It should be noted that with the designs as shown in FIGS. 12A and 12B,the effect of extending the depth of field (or focus) applies to boththe central vision and also the paracentral (and/or peripheral) visionalthough the extension in the paracentral (and/or peripheral) retina canbe different than that in the central retina.

FIG. 12C shows a comparison of the sharp focus image positions of someoptical environment objects (M, P, Q as central objects and X, Y, Z asperipheral objects) as they land on the retina in the case of an eyewearing an IRODR spectacle disclosed in FIGS. 12A and/or 12B as shown inthe upper portion of FIG. 12C, versus the case of an eye wearing aconventional single element vision correction spectacle lens as shown inthe lower portion of FIG. 12C. In both cases, it has been assumed thatthe eye is fixating on the central object P. In the IRODR case, thecentral optical environment objects M, P, and Q are imaged to thecentral retina region with their sharpest focus image positions closestto the central retina and their relative distances from each othershort. The paracentral optical environment objects X, Y and Z are imagedto the paracentral retina region with their sharpest focus imagepositions still very close to the paracentral retina, but may not be asthe same as in the central retina case. In comparison to the singleelement vision correction lens case as shown in the lower portion ofFIG. 12C, the same central optical environment objects M, P and Q, whenimaged to the central retina region, will have their sharpest focusimage positions more separated from each other around the central retinacompared to the IRODR case. Similarly, the same paracentral opticalenvironment objects X, Y and Z, when imaged to the paracentral retinaregion, will have their sharpest image focus positions also moreseparated from each other around the paracentral retina compared to theIRODR case.

In one embodiment, the peripheral zone of the negative lens can have agradually less and less curved surface while the peripheral zone of thepositive lens also has gradually less and less curved surface. As thecurvature reduces towards the peripheral edge, the design can be suchthat while the overall IRODR combination net optical refractive power isthe same as a single element vision correction lens would provide to thepatient, the depth of field (or focus) enhancement effect will graduallydecrease and the optical demagnification effect as seen by otherobservers when they look at the patient eye through the IRODR spectaclelens will gradually become that of a single element vision correctionlens.

This can be achieved by keeping the difference in the magnitude of thefocal lengths of the negative lens and positive lens to be about thesame so the separation or gap distance between the negative lens and thepositively lens remains the same, while the ratio of the focal lengthmagnitude of the positive lens over that of the negative lens graduallyreduces from the highest value at the center toward a value closer toone at the peripheral edge.

In such a way, the pupil of the wearer's eye will be effectively reducedto help enhance the depth of field (or focus) for central vision, whilethe outer portion of the eye (from iris, to limbus, to eye lids,schelera and canthus) will gradually have close to normal perceived sizeas a single element vision correction lens would have when viewed byoutside observers. A huge upside of such a design is that cosmetically,the wearer's eye when viewed by an outside observer will not be too muchminimized or distorted so the spectacle will be more acceptable by apotential wearer.

In another embodiment, the design is such that while the sphericalequivalent image shell is formed in front of the paracentral retina, thesagittal image shell is sharply focused on the paracentral retinal area.These various means should be considered as different embodiments of thepresent invention.

Note that although the peripheral zone can have the same effect as theparacentral zone (i.e. forming an image shell in front of the peripheralretina), in other embodiments, the design can be such that only theparacentral zone outside the central zone has the design to form animage shell in front of the paracentral retina while the peripheral zonehas a different profile and/or effect. This is because the paracentralretina is most effective in terms of controlling the elongation of theeye, while the peripheral retina is mainly used to sense the presenceand movement of peripheral optical environment objects.

In terms of the difference between the peripheral zone and theparacentral zone, the peripheral zone can have many other possibledesigns. For example, the peripheral zone can function to just correctthe refractive error as a single element lens does. In such a case, asone embodiment, the positive lens can have a peripheral zone that islike a parallel plate piece of glass and the peripheral zone of thenegative lens can have a negative refracting power almost the same as asingle element prescription lens. Again, such a design will becosmetically more acceptable to a potential wearer because theperipheral zone of such an IRODR design will have the same opticalmagnification or demagnification as a single element vision correctionlens would have when the wearer's eye is viewed by an outside observer.

Also the peripheral zone can have a prism structure like an annularaxicon lens. As such, the function of the peripheral zone is to purelyexpand the field of view and FIG. 13 shows such an embodiment. Note thatthe peripheral zone of the either the negative lens 1306 or the positivelens 308 or both can be made with a prism structure like an annularaxicon lens. So expanding the field of view can be accomplished with theprism structure 1362 of the peripheral zone 1365 of the negative lens1306 alone or that of the positive lens 308 alone or those of both thenegative lens 1306 and the positive lens 308.

Note also that in these designs, the optical magnification ordemagnification from the central zone to the paracentral zone to theperipheral zone can change continuously or discontinuously and as aresult certain degree of optical distortion is intentionally created.This intentional distortion is something that ordinary single elementvision correction lens will try to avoid but in this invention, it isused to bring benefit to presbyopia treatment and myopia progressioncontrol.

Note also that the transition in the optical refraction profile ordistribution can be gradual or non-gradual and discontinuous orcontinuous. There can be multiple steps or multiple gradual transitions.In addition, the refractive index of the lens material can also bevarying which include design of gradient refractive index distributions.

In one embodiment, the relative net refractive power increasescontinuously or discontinuously across a first transition zone from thecentral zone to the paracentral zone and then further increasescontinuously or discontinuously across a second transition zone from theparacentral zone to the peripheral zone. In another embodiment, therelative net refractive power increases continuously or discontinuouslyacross a first transition zone from the central zone to the paracentralzone and then decreases continuously or discontinuously across a secondtransition zone from the paracentral zone to the outer edge of theperipheral zone.

Since the increase in the depth of field (or focus) and the need to makenearby object optically pushed away is only needed for the central andpart or all of the paracentral region, and the peripheral region of theretina is meant to sense presence or movement of peripheral objects, akey benefit of using the peripheral zone to expand the field of view isthat with the central zone fully correcting the refractive error(s) andthe paracentral zone creating an image shell in front of the paracentralretina that is most effective in controlling myopia progression, byexpanding the field of view to create a desired degree of tunnel visionthat covers the needed field of view, the eye will no longer tend torotate in trying to look at a peripheral object. Instead, the designwill likely force the patient head to move to re-center the object inorder to look at the object more clearly. As a result, the design willbe more effective in myopia progression control.

Note that the peripheral zone can also have a changing net refractivepower that either gradually reaches a value as a single element visioncorrection lens would provide, or gradually reaches a value that isgreater than a single element vision correction lens would provide, orgradually reaches a value that is less than a single element visioncorrection lens would provide. Depending on which area of the retina ismost effective in terms of controlling myopia progression by renderingmyopic defocus on such area, the paracentral zone size and degree ofoverall refractive power can be controlled accordingly. It is evenpossible that the overall size of the negative lens and the positivelens can be different.

Let us now take a look at one design that may benefit presbyopiatreatment. Assuming that a presbyopic eye originally has sufficientfield of view coverage (i.e. there is no tunnel vision), then there isno need to use the IRODR spectacle to increase the field of viewcoverage. There is also no need to introduce myopic defocus on theparacentral or peripheral retina like in the case of myopia progressioncontrol. As such, the paracentral surface curvature designs of the twolenses can be different. In one embodiment, the paracentral andperipheral zones have net aspherical or freeform optical designs suchthat minimum spherical aberrations are introduced. In addition, if thereis a need for astigmatism correction, a cylinder design can also beemployed (for example on one or both of the outer surfaces).

FIG. 14 shows one embodiment in which the negative lens 1406 has a planoor less curved front surface 1452 while the back surface 1454 is asubstantially concave aspherical surface for the central and paracentralzones (1361 and 1363) such that these two zones (1361 and 1363) do notinduce negative spherical aberration. The positive lens 1408 has aconvex aspherical front surface 1456 for the central and paracentralzones (1361 and 1363) and a plano or substantially less curved backsurface 1458 such that the central and paracentral zone (1361 and 1363)of the lens does not induce positive spherical aberration.

In the peripheral zone 1365 the net refractive power of the IRODRcombination gradually reduces to a value as that of a single elementprescription lens would have for the conventional treatment of myopia.If the presbyopic eye is emmetropic, there is no needed visioncorrection so the refractive power of the IRODR combination is basicallyabout zero across the whole IRODR area. This design will result in agradual change in the optical magnification/demagnification and depth offield (or focus) from the paracentral zone 1363 to the edge of theperipheral zone 1365. Since the increase in the depth of field and theneed to make nearby objects optically pushed away is only necessary forthe central fovea or macula, and the peripheral region of the retina ismeant to sense the presence and/or movement of peripheral objects, theparacentral zone 1363 thus serves the function to reduce sphericalaberration, while the peripheral zone 1365 will remove the possibilitythat double images of a peripheral object (one through the peripheralregion 1365 of the IRODR spectacle and the other from outside thespectacle frame border) will be formed on the peripheral retina. Thedesign will be ideal for the treatment of a myopic presbyopic eye. Inthe case of an emmetropic presbyopic eye, the net refractive power atthe peripheral edge should be zero.

Again, the same overall refraction effect can also be achieved bymanipulating the optical interface design(s) of any one or more of theoptical interfaces or even the refractive index distribution of one orboth lenses. It is preferable to make the negative lens 1406 less curvedin the paracentral zone 1363 and especially the peripheral zone 1365 assuch a design will enable one to reduce the overall thickness of thenegative lens.

The design may need to require the negative lens 1406 to have a largersize than the positive lens 1408. Another possible embodiment is todesign the IRODR spectacle to have panoramic curved peripheral zones assome sport sun glasses have.

FIG. 15 shows another embodiment of the present invention. In thisembodiment, the back surface 1554 of the negative lens 1506 is concavelycurved in such a way that from the central zone 1361 to the paracentralzone 1363 and then to the outer peripheral zone 1365, the relativeoverall refractive power has a net add power in the paracentral zone1363 relative to the central zone 1361 and then a net decreasing powerin the peripheral zone 1365 relative to the paracentral zone 1363. Thepurpose of making the peripheral zone 1365 having a net relativenegative power is to expand the field of view.

Another way to achieve the same effect is to make the peripheral region1365 of the positive lens 1508 gradually less curved or even graduallyconcavely curved and at the same time make the peripheral zone 1365 ofthe negative lens 1506 less curved so the overall thickness of thenegative lens 1506 is reduced. In such a case, while the central zone1361 of the IRODR combination corrects the refractive error(s) with animage of a distant or intermedia object sharply focused on the fovea ormacula of a myopic eye like a single vision correction lens does. Theparacentral zone 1363 makes the image of an object myopically defocusedon the paracentral retina (i.e. the image shell is in front of theparacentral retina), and the peripheral zone 1365 can negatively bendany incident light rays more to expand the field of view.

To avoid double image formation on the peripheral retina of peripheralobjects, the spectacle design can be such that the field of view outsidethe refractive combination of the IRODR spectacle is blocked. Thebenefit of such a design is that it can limit the tendency of eye ballor ocular movement relative to the IRODR spectacle because some degreeof tunnel vision is intentionally created while a wide enough field ofview is covered with only the central and paracentral region of theretina being able to receive light. In one embodiment, the peripheralregion 1365 of the IRODR combination is apodized such that there is agradual transition from full transparency at the border between theparacentral zone 1363 and peripheral zone 1365 and then to totalopaqueness at the outer edge of the peripheral zone 1365.

Note again that the peripheral zone of the IRODR spectacle can be bentin the same way as a panoramic sun glass to not only cover a widerperipheral view without being blocked by the lens frame, but also makethe overall spectacle look more like an augmented reality goggle soyoung children will be excited to wear their spectacles.

FIG. 16A shows another embodiment in which the peripheral zone 1365 ofthe negative lens 1606 a is made with a Fresnel lens design so theoverall thickness of the negative lens 1606 a is reduced while the samegoal to allow the peripheral portion of the retina to sense the presenceof any peripheral object, especially the movement of peripheral objectis achieved. Note that the same concept can be applied to the design ofthe positive lens 1608 as well as both lenses so the overall thicknessof the IRODR combination can be made even thinner. By doing so, an evenshorter focal length magnitude (or stronger refraction) of both thenegative lens 1606 a and the positive lens 1608 can become practical forselection in terms of combining them to make a compact IRODR spectacle.

FIG. 16B shows an embodiment in which the peripheral zones 1365 of boththe negative lens 1606 b and the positive lens 1608 b are all made withFresnel lens designs. This design can allow the use of stronger powernegative lens 1606 b and positive lens 1608 b so the overall thicknessof the IRODR combination can be further reduced when compared to FIG.16A while the same ratio of the focal length magnitude of the negativelens 1606 b over that of the positive lens 1608 b for the central zone1361 can be either maintained or changed gradually or step-wise to adesired value.

FIG. 16C shows an embodiment in which both the paracentral zone 1363 andthe peripheral zone 1365 of both the negative lens 1606 c and thepositive lens 1608 c are all made with Fresnel lens designs so theoverall thickness of the IRODR combination can be even further reduced.In this design, even stronger power negative and positive lenses can beused while the same ratio of the focal length magnitude of the negativelens 1606 c over that of the positive lens 1608 c for the central zone1361 can be either maintained or changed gradually or step-wise to adesired value.

Note that discussions made on the curvature of the negative lens backsurface and the positive lens front surface relating to the paracentraland peripheral zones for both presbyopia treatment and myopiaprogression control can all be applied to the various Fresnel lensdesign cases. It should be noted that all the above IRODR lenscombination designs can be mounted on a frame in the same way that atypical single element vision correction lens or a reading glass or asun glass would be mounted except that the overall thickness of theIRODR spectacle will likely be slightly thicker. It should also be notedthat with the use of light weight and high refractive index material tomake the IRODR lenses, together with the use of light weight spacers andthe lens mounting frames, the overall weight of the spectacle will notbe significantly increased. FIG. 17 shows such a case where thepresently disclosed IRODR lens combination 1702 is mounted on aspectacle frame 1772.

In another embodiment, a bigger opaque band 1874 is deliberately createdby making lens mounting section wider. This embodiment can remove doubleimage of peripheral objects for the case in which the field of view isexpanded and tunnel vision is created to make myopia progression controlmore effective. The width of the opaque region 1874 can be such that thefield of view border as seen through the IRODR lens combination is justconnected to the field of view outside the lens mounting frame. FIG. 18shows such an embodiment. It should be noted that there are differentways to create tunnel vision. For example, the connecting tube portionof the lens mount that holds and spaces the two lenses can be madeopaque. An apodized tunnel vision can also be created by making theregion that would create double image of peripheral objects to havegradually darkening opaqueness.

In another embodiment, the design of the IRODR spectacle can alsoinclude a design similar to what a conventional bifocal lens or aconventional progressive addition lens would provide. In such a case,the overall refraction of the spectacle is such that as the patientwearing such an IRODR spectacle looks slightly downward to use the lowerportion of the spectacle to look at nearby objects, the overall netrefraction of the spectacle will make the nearby object better in focuson the central retina. FIG. 19 shows such an embodiment where inaddition to those various designs discussed above, there is a netoverall relative addition of plus refraction power in the shaded region1992 relative to that in the center and upper portion of the IRODRspectacle. The transition to the add power can be discrete as in atypical bifocal lens case or gradual as in a typical progressiveaddition lens case.

Note that the bi-focal or progressive addition design can also be thatthe upper and central zones of the IRODR lens combination are configuredto provide a net central and upper refractive power that corrects therefractive error(s) (including astigmatism) of a patient eye for distantor intermediate vision. And the lower zone(s) 1992 or a selected area inthe lower zone of the IRODR combination have a net refractive power thatis higher than the net refractive power of the upper and central zone tocorrect the refractive error(s) of a patient eye for near vision. In thebi-focal case the transition of the net refractive power from the upperand central zone to the lower zone is discontinuous. In the progressiveaddition case, there is a transition region linking the central zone andthe lower zone and the transition of the net refractive power from theupper and central zone to the lower zone is continuous.

In addition to the above, the design can further be such that thecentral zone of the IRODR lens combination are configured to provide anet central refractive power that corrects the refractive error(s)(including astigmatism) of a patient eye for distant or intermediatevision. Outside the central zone, there is a paracentral zone that linksto the upper peripheral zone and the lower zone, the net refractivepower gradually increases in the paracentral zone from the central zoneto create image shell in front of the paracentral retina when thepatient looks straight at far or intermediate objects. In addition, thelower zone(s) or a selected area in the lower zone of the combinationhave a net refractive power that is higher than the net refractive powerof the upper and central zones to correct the refractive error(s) of apatient eye for near vision. And within the lower zone or the selectedarea in the lower zone, there can also be gradual increase in the netrefractive power towards the outer directions.

Note that the designs of the lower portion of the IRODR combination fornearby object can also be prismatic by itself or in addition to bifocalor progressive addition features with a prismatic power adapted to achild's physiology such as esophoria or exophoria. In addition, thepower addition value can be different depending on the special case of aparticular child although a 2.00 D addition has been shown to be themost efficient. In one embodiment, the discontinuity in refractive powertransition is made on one of the two inner lens surfaces so the step isnot on one of the two outer surfaces. In another embodiment, the lowernear vision portion has a different optical minimization percentage thanthat of the upper distance vision portion.

Note that many different single element vision correction and readingglass lens spectacle designs can be directly applied to the presentlydisclosed IRODR spectacle designs. It should be noted that the presentinvention involves a pair of IRODR lens combinations that are mounted ona lens mounting frame to be worn by a patient to treat presbyopia andmyopia progression with the central zone of the pair providingcorrection of refractive errors. There needs to be symmetry between thepair in terms of the frame and IRODR design.

It should also be pointed out that in terms of changing the separationdistance between the two lenses, in addition to continuous changes,stepped discontinuous changes can also be employed in the same manner as0.25 Diopter steps for conventional prescription lens designs.

In addition, one embodiment of the present invention is to automaticallychange the separation distance between the two lenses such that theoverall net central refractive power of the IRODR combination canautomatically adapt to indoor versus outdoor lighting conditions toenable automatic near versus far distant vision correction.

In this respect, light sensor(s) that is (are) responsive to surroundinglight level and/or light spectral distribution can be designed insidethe IRODR lens combination or on the spectacle frame of the invention.Solar cell(s) or battery (batteries) or replaceable battery (batteries)can also be designed inside the IRODR lens combination or on (or in) thespectacle frame to provide power to the light sensors as well as todrive a mechanism that can actuate a change in the separation distancebetween the two lenses. Note that an advantage of designing the lightsensor and the solar cell inside the IRODR lens combination is that thelight sensitive area can be kept relatively clean by the patient simplybecause the patient will tend to clean the spectacle lens regularly inorder to see object clearly through the spectacle.

FIG. 20 shows an embodiment in which solar cells 2092 and light sensors2094 are embedded in the frame 2072 of the IRODR spectacle together withelectronics, firmware and an actuation mechanism (not shown) todetermine if a patient wearing the spectacle is indoor or outdoor andhence to keep or actuate a change in the separation between the twoIRODR lenses. Preferably, the mechanism used to activate the change inthe separation distance between the two lenses is passive in the sensethat once latched into position there is no energy need to maintain theposition.

It should be noted that with the presently disclosed automatic actuationmechanism, for presbyopia treatment, a spherical negative lens and aspherical positive lens will be sufficient although aspheric designs canbe better. In other words, there is no absolute need for the IRODR lenscombination to have a paracentral and/or a peripheral zone that hasrelative net add or subtract refractive power(s) with respect to thecentral zone. However, for myopia progression control, it will be betterfor the IRODR lens combination to have a paracentral and/or a peripheralzone that has relative net add or subtract refractive power(s) withrespect to the central zone, although myopia progression can stilllikely be controllable even without the relative net add or subtractrefractive power(s).

It should be noted that the present invention should be interpreted ascomprising two refractive elements that are separated but close enoughto enable a practical compact spectacle design, with the first elementhaving a strong negative refractive power in its central zone and thesecond element having a less strong but positive refractive power in itscentral zone. The paracentral and peripheral zones can have differentspatial refraction profiles or distribution as discussed above.Therefore, the function of the first element can also be realized withonly one curved optical interface and the function of the second elementcan also be realized with only one curved optical interface. FIG. 21shows one embodiment in which one relatively thick optical medium 2102is shaped such that its central front surface 2154 is strongly concavelycurved to function as a negative refracting element and its back surface2156 is less strongly convexly curved to function as a positiverefracting element. The thickness of the optical medium now functions toseparate the negative refractive element from the positive refractiveelement. Such a design can also have a central zone, a paracentral zoneand a peripheral zone with all the various properties discussed aboveincluded and the design should therefore also be considered as withinthe scope of the present invention. In one embodiment, the negative andpositive refractive powers of the first and second refractive elementcan be achieved with nano-structured metamaterial so the surfaces arerelatively flat. With such a design, the concept can be applied tocontact lens designs as well.

In addition, the scope of the invention should also cover the case wherethere are more than two refracting elements as long as there is a strongnegative refractive element in front of a less strong positiverefractive element. For example, FIG. 22 shows an embodiment where threeoptical interfaces are employed and the intermediate optical interface2257 serves the function to provide chromatic and spherical aberrationcorrections. In this case, the front curved surface 2254 and the backcurved surface 2256 will likely have different curvatures as compared tothose in FIG. 21.

Although various embodiments that incorporate the teachings of thepresent invention have been shown and described in detail herein, thoseskilled in the art can readily devise many other varied embodiments thatstill incorporate these teachings.

What is claimed is:
 1. A wearable optical device configured to increasea Resolvable Object Distance Range (RODR) for a plurality of objectslocated along a visual angle distance by optically pushing a nearbyobject further away along the visual angle distance thereby reducingfocus accommodating demands when a user is visually fixating on a nearbyone of the plurality of objects.
 2. The wearable optical device of claim1 wherein the reduction of focus accommodating demands also reduceseyeball-elongation signal generation of the user to control myopiaprogression of the user.
 3. The wearable optical device of claim 1further comprising bringing a distant object closer along the visualangle distance.
 4. The wearable optical device of claim 1 comprising: acentral zone; and a non-central zone wherein at least one portion of thenon-central zone has a net refractive power that is different from a netrefractive power of the central zone.
 5. The wearable optical device ofclaim 4 wherein a non-central one of the plurality of nearby objects isoptically pushed to land forward or anterior with respect to anon-central region of a retina of the user when the user is visuallyfixating on a central nearby object.
 6. The wearable optical device ofclaim 4 wherein the net refractive power of the non-central zone ishigher than the net refractive power of the central zone for a myopic oremerging myopic user.
 7. The wearable optical device of claim 4 whereinthe net refractive power of the non-central zone is lower than the netrefractive power of the central zone for a hyperopic user.
 8. Thewearable optical device of claim 4 wherein the non-central zone of theoptical device includes a paracentral zone and a peripheral zone, andwherein the paracentral zone corresponds to a paracentral region of theretina coupled to a higher density of ganglion cells than a peripheralregion of the retina.
 9. The wearable optical device of claim 1 whereinthe optical device includes a hybrid multi-element lens combinationincluding: a negative refractive element having an optical axis; and apositive refractive element configured to be aligned with the negativerefractive element along the optical axis.
 10. The wearable opticaldevice of claim 9 wherein the negative refractive element is a plano andaspherical concave lens, wherein the positive refractive element is aplano and spherical convex lens, and wherein each respective planosurface is an exterior surface.
 11. The wearable optical device of claim9 wherein the negative refractive element and the positive refractiveelement are separated from each other along the optical axis at aseparation distance suitable for mounting on a spectacle.
 12. Thewearable optical device of claim 1 further comprising a spectacle frame.13. The wearable optical device of claim 1 further comprising a stronglycurved surface.
 14. The wearable optical device of claim 13 wherein thestrongly curved surface has a non-central zone is a Fresnel surface. 15.The wearable optical device of claim 8 wherein the net refractive powerchanges continuously from the central zone to the paracentral zone. 16.The wearable optical device of claim 8 wherein the net refractive powerchanges continuously from the paracentral zone to the peripheral zone.17. The wearable optical device of claim 8 wherein at least one of theparacentral and peripheral zone is formed with at least one ofapodization, gradual transparent-to-opaque-transition, and gradualtransparent-to-opaque-to-transparent transition.
 18. The wearableoptical device of claim 4 wherein the central zone includes at least oneaspherical refractive surface configured to correct at least one ofastigmatism and any other higher order aberrations.
 19. The wearableoptical device of claim 11 wherein the separation distance between thenegative refractive element and the positive refractive element isadjustable to enable fine tuning and control of a net sphericalrefractive power.
 20. The wearable optical device of claim 11 furthercomprising: an optical sensor configured to detect a light intensity;and an actuation mechanism configured to adjust a separation between thenegative refractive element and the positive refractive element.
 21. Thewearable optical device of claim 9 wherein a focal point (F_(A)) of thenegative refractive element and a focal point (F_(B)) of the positiverefractive element are offset with respect to each other along theoptical axis.